Enter each of the following codes on the Cheat screen. To access this screen, press the R Button and Z Button simultaneously at the Main Menu. Once you've input the code press the Start button to activate it. If you did it correctly, you will hear a "boiing" sound. During game play, if you pause, you will see a new option called Cheat Menu, accessing this menu can enable or disable any code you have entered.

Code - Function 

THEUNIVERSE - All tracks available 
HAPPYHEADS - All hidden characters but one 
ENTAROADUN - Iggy's girlfriend and no other characters 
JUMPAROUND - Level select [Note] 
ICEPRINCESS - Ice platforms 
GOOEYGOOGOO - Gooey platforms 
GOOEYICEPRINCESS - Icy and gooey platforms 
SWOPSHOP - Mix and match mode 
2TIMES - Turbo mode 
GOBABY - Full turbos 
ROLFHARRIS - Black and white mode 
PENCIL - Pencil and ink mode 
OHMY - Random bombs 
TOOMUCHFUN - Bouncy physics on your balls 
MICROBALLS - Tiny reckin' balls 
TOOMUCHPIE - Fat reckin' balls 
NONSTOP - Non-stop roller ball 
2ROKTOO - Enable Turok 2 graphic effect engine 

Note: Pause the game to access the level selection option.

Bonus Characters:-  To unlock each bonus character finish every race in first place.
Full Boost:-  To get a full boost slightly tap Jump while standing on a boost platform.

Game Shark Codes

Infinite Credits - 800BDEA5 0005 
No Credits - 800BDEA5 0000 
Unlock All Bonus Characters - 810C632E FFFF 
Unlock All Courses - 
810CCDF2 0B00 
810CCDF4 0B00 
810CCDF6 0B00 
Gold Medals Won Modifier P1 - 810D8EF0 ???? 
Level Modifier - 800CCF69 00?? 
Start on Level Modifier - 
D00CCF69 0000 
800CCF69 00?? 
Always Have Points Modifier P1 - 810D8EE0 ???? 
Always Have Points Modifier P2 - 810D8EE2 ???? 
Always Have Points Modifier P3 - 810D8EE4 ???? 
Always Have Points Modifier P4 - 810D8EE6 ???? 
Have Cheats Modifier 1 - 800CCF89 00?? 
Have Cheats Modifier 2 - 800CCF8A 00?? 
Have Cheats Modifier 3 - 800CCF8B 00?? 
Enable Cheats Modifier 1 - 800CCF91 00?? 
Enable Cheats Modifier 2 - 800CCF92 00?? 
Enable Cheats Modifier 3 - 800CCF93 00?? 
Quantity Digits to Accompany Cheat Modifier 1 Codes - 
01 - 2X Turbo Time 
02 - Blue Balls 
04 - Explosive Mode 
08 - Full Turbo 
Quantity Digits to Accompany Cheat Modifier 2 Codes - 
01 - Ice Mode 
02 - Slime Mode 
04 - Just Bombs 
08 - Sudden Death 
10 - Bomb Physics 
20 - No Weapons 
40 - Roll Mode 
80 - Bomb Pickups 
Quantity Digits to Accompany Cheat Modifier 3 Codes - 
01 - All Characters 
02 - All Worlds 
04 - Level Select 
08 - Mix 'N' Match 
10 - Pencil 
20 - Fat Mode 
40 - Tiny Mode 
80 - Dark City